Organic light emitting diode (OLED) display is one of the recent popular research focuses. As compared to Liquid Crystal Display (LCD), OLED display has advantages of low energy consumption, low manufacturing cost, being self-luminous, wide viewing angle and quick response and so on.
In the existing display devices, each row of pixel units is connected with a scanning signal line and a light emitting control signal line. In the prior art, in order to narrow the frame of a display, the GOA unit of a scanning signal is usually adopted to drive the scanning signal line, and the GOA unit of a light emitting control signal is used to drive the light emitting control signal line. A GOA circuit is usually formed by a plurality of cascaded GOA units. At the time of booting or waking up the sleep mode, as illustrated by FIG. 1(a) and FIG. 1(b), before each cascaded GOA unit driving the corresponding pixel circuit as shown in FIG. 1(a), the driving transistor Md in the pixel circuit is in the floating state. At this moment, the driving transistor Md is prone to the disturbance of other signals, so that some driving transistors Md in the pixel circuit are turned on. In this case, a current flows through the lines of the transistors Md and M6, resulting in the pixel turned on by the driving transistor Md giving out incorrect light by mistake.
Moreover, as the signal of the high voltage terminal VDD is input earlier than that of the low voltage terminal VSS, and there is a current in the lines of the transistors Md and M6 within the pixel circuit turned on by the driving transistor Md, the magnitude of voltage at the low voltage terminal VSS will be raised, damaging or destroying the power sources that supply signals to the high voltage terminal VDD/low voltage terminal VSS. Under this circumstance, the SSD (start-up short detection function) of the circuit will initiate the function of protection, cut off the power source automatically, and this will cause the screen is failure to display normally.